Fabrication of large grain NdBaCuO by seeded melt growth

Abstract

Large, single grain NdBaCuO (NdBCO) composite samples of NdBa 2Cu 3O 7−δ (Nd-123) containing 15 and 20 mol. % non-superconducting Nd 4Ba 2Cu 2O 10 (Nd-422) phase inclusions have been fabricated successfully by a variety of techniques based on top-seeded melt growth under reduced oxygen partial pressure. Specifically, individual grains up to 2 cm in diameter have been grown using (100) oriented MgO seeding, self (NdBCO) seeding at elevated temperature and self-seeding of Ag and Au doped precursor pellets. The latter exhibit a reduced peritectic decomposition temperature compared with the undoped compound. These techniques, which vary in degree of difficulty and hence reliability, yield grains with a range of microstructural homogeneity. This paper describes the general aspects of large NdBCO grain fabrication and presents the results of the different fabrication techniques.